Sampling and data handling

Poux and Fayoulle [3] summarized the results of other researchers investigating the effect of sample size on assessment of the quality of a mixture. The size of the sample must be adapted to the dimensions of the powder material, whose distribution in the mixture must be determined. 

Pharmaceutical and medical applications of near-infrared spectroscopy 

The nature of individual particles and their size in comparison with the size of the sample must be considered. The size of a sample should correspond to the use of the mixture. The reason for unit-dose samples in powder blend testing is to ensure that individual doses contain the intended amoimt of each constituent. 

The choice of an endpoint algorithm must nevertheless be dictated by the product of interest, the particular characteristics the delivery forms should have, and the purpose of blending. No one algorithm is adequate for all formulations. However, with the increase in intricacy of the blending systems (multiple sensors, multiple parameters to follow, etc.), the decision process increases in complexity with not only calibration maintenance issues to consider, but also calibration transfer and the relevance of the desired final product properties [36,38]. 

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Most testing labs will already have detailed mechanisms in place for sample and data handling, which are GLP-compliant based on a network of SOPs covering all aspects of GLPs. It is still important, however, that audits are carried out by the sending laboratory before final selection of a testing lab is made, to ensure that the GLP implementation, required instrumentation, handling of samples, and data are acceptable. 

System Suitability System suitability refers to the validation of all components of an analysis system taken as a unit, a "system." For example, the analysis of an environmental water for pesticide residue involves a "method," which includes sampling (must represent the water in question), sample handling (e.g., what container is appropriate), sample preparation (perhaps an extraction process that includes the glassware, technique, timing, etc.), standards preparation (pipets, flasks, technique, etc.), injection technique, the instrument, and data handling (computer hardware and soft-... 

Work by Catanzaro et al. in 1968 (6) led to a new analytical procedure permitting the measurement of isotopic ratios to about 0.05% (95% L.E.) this resulted in the availability of three standard reference materials, so that results could be placed on an absolute basis. This procedure, still the most precise and accurate one available, requires about 1 mg of lead for an analysis. A second procedure (7) has been developed which utilizes silica gel as an ionization enhancer. This method permits the measurement of isotopic ratios to about 0.1% (95% L.E.), but it requires only 0.1 /xg of lead per analysis. In addition, the instrumentation and data handling have been vastly improved so that many samples can be studied quickly and conveniently. 

Speed of Analysis. The speed with which many immunochemical analyses can be completed illustrates a major advantage of immunochemical procedures. Immunochemical assays are most time and cost effective when the sample load is large. Parker (4) estimated that a single technician could perform 100-5000 radioimmunoassays per day with little or no assay automation in comparison to 20-40 GLC assays (3). Numerous inexpensive systems are available to decrease analysis time. These systems may include solid phase separation techniques, automatic dispensers, test tube racks which will fit directly into a centrifuge and/or scintillation counter, and data handling systems. Alternatively, there are fully automated systems based on RIA or ELISA which require very little operator attention and which handle 25-240 samples/hr. Gochman and Bowie (81) have outlined the basis of operation and summarized the features of automated RIA systems and extensive literature is available from the manufacturers. 

Within the entire workflow described above the standardization of sample preparation [implementation of standard operating procedures (SOPs)], analyzing procedures and data handling will assure the comparability of results within the network as well as with results outside the consortium. Thus, the standardization is essential for efficient networking. 

Many advances have been made in recent years in chromatographic instrumentation and data handling including important advances in automation. However, for many methods, equally important is the sample preparation procedure. These are sometimes complex, and are often the key step in a method, but perhaps receive less attention than is warranted. The optimisation of sample preparation and the development of... 

The thermogravimetric analyser is a SDT-DTA from TA Instruments, supported by an HP PC and software for control and data handling. The system consists of a dual beam horizontal balance. Each arm holds one cup and there is one thermocouple under and in contact with each cup. One cup contains the char sample and the other cup is empty, used as a reference for temperature effects. Detailed description of the instrument can be found somewhere else. Ceramic cups were used for most of the experiments. The apparatus has been recently upgraded and it was possible to operate in a TGA-DSC mode. Therefore, not only the temperature and the weight have been registered but also the heat demand of the process. Table 2 and Table 3 show the experimental matrix for this work. 

G.29 R. Jenkins and J. L. DeVries. Practical X-Ray Spectrometry, 2nd ed. (New York Springer-Verlag, 1969). Experimental and data-handling aspects. Quantitative analysis, sample preparation, and trace analysis. Energy-dispersive methods not included. 

The authors would like to thank Douglas C. Beckwith and Robin G. Roaldson for their assistance in sample preparation and data handling. 

Assay application. At this point major differences appear between the historical use of clinical immunoassays and the potential applications of environmental and pesticide immunoassays. Most clinical assays have been applied to simple or well defined and consistent matrices such as urine or serum. In contrast, most matrices likely to be analyzed for pesticides are more complex, less well defined, and more variable. The potential for serious problems with matrix effects in the environmental field is far greater than most clinical immunoassays have encountered. The application of immunoassays to environmental analysis requires sampling strategies, cleanup procedures, and data handling fundamentally similar to those presently in use in any good analytical lab. The critical factor in the success of immunochemical technology will likely be competence... 

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